The present invention relates to characterizing components of a system, and more particularly to characterizing electrical networks using various parameters. As digital signals move to communication in gigahertz and gigabit ranges, interconnects become more important in enabling reliable system performance. Signal integrity issues such as reflection, crosstalk, frequency dependent transmission line loss, and the like can significantly degrade system performance and reliability. The ability to simulate and accurately predict the effect of such signal integrity issues is part of designing a system.
Network analyzers are used to characterize active and passive components. Such components may include interconnects, and these components can have one port (input or output) or many ports. The ability to measure the input characteristics of each port, and the transfer characteristics from one port to another gives a designer needed information. A vector network analyzer (VNA) is one type of network analyzer that can measure integrity issues over wide frequency ranges. VNAs are often used during design and manufacture to measure and display complete amplitude and phase characteristics of an electrical network (i.e., system components). These characteristics include scattering parameters (S-parameters), standing wave ratios (SWR), insertion loss or gain, delay return loss, reflection coefficient and the like.
While such VNAs and other network analyzers may be used during design, they are often expensive and difficult to use. Furthermore, such network analyzers require presence of actual devices. Accordingly, during a design phase, it is desirable to perform simulations similar to characterizations that may be done on network analyzers. Various computer programs exist to perform such simulations for characterizing electrical networks. Thus a designer will often use a simulation to test and determine characteristics of a proposed component before incorporation into a system.
Using such a simulation, a designer typically calculates a differential S-parameter by taking single-ended parameters and manually manipulating the single-ended parameters using appropriate mathematics to convert them into the differential parameter. For example, a designer will print real and imaginary portions of single-ended S-parameters, insert them into a spreadsheet or math program, perform appropriate mathematical functions and plot results as a function of frequency. However, there is no easy way to obtain differential parameters within a simulation program. Accordingly, a need exists to directly obtain differential parameters, particularly in a simulation program.